Post-Earthquake Investigation of Several Geosynthetic Reinforced Soil Retaining Walls and Slopes During Ji-Ji Earthquake of Taiwan - Reinforced Soil Engineering: Advances in Research and Practice - page 304

with on-site soils. The slope was designed for seismic stability with a seismic
coefficient of 0.15. An HDPE geogrid was used. The spacing of reinforced slope
was 50 cm, and the reinforcement was 18.5m long with an overlapping length of
2.5m.
Note that the width of this slope was less than that of Chi-Nan University
and the orientation was different as well. This reinforced slope behaved as an
archlike structure when viewed along its width (see Chou et al., 1994). The end
effects could have improved the stability.
6 CONCLUSIONS
The Ji-Ji earthquake caused some damage to the geosynthetic reinfoced soil
structures in Taiwan. A few modular block geosynthetic reinforced soil retaining
walls and reinforced slopes were damaged. Some of the lessons learned from the
post-earthquake investigation are as follows:
1. Taiwan is located in a seismically active region, but it is not clear if
seismic design was conducted for most reinforced soil structures.
While the design of geosynthetic reinforced soil structures is believed
to be very conservative in other parts of the world, the design
conditions are more severe in Taiwan because of the topography and
economic reasons, such as the use of on-site backfill soil and above-
normal-height stacked walls and slopes.
2. The seismic design of reinforced soil structures has gained attention
worldwide only in recent years. However, most of the seismic design
procedures do not incorporate compound failure analysis. The cracks
behind the wall indicated that a few of the structures suffered
compound failure or did not have adequate global stability.
3. The failure of modular block reinforced soil retaining walls could be
attributed to a lack of professional design as seen by arbitrary spacings
used in several of the reinforced soil retaining walls, and with a mixture
of unreinforced and reinforced retaining walls within a common
structure.
4. The connection between the modular blocks and reinforcement is vital
for a satisfactory performance of the structure under high seismic load.
The strength and stiffness of the pins, and that of the reinforcement in
the transverse direction, should be large enough to sustain the dynamic
earth pressure since the collapse of the blocks led to failure of the wall.
5. The inertia of the modular blocks led to excessive deformation under
seismic excitation. The structures, such as the lampposts, should not be
installed at the vicinity of the modular block walls.